Kernel Mode Driver Framework >> C/C++ (PNP) >> File

WdfDeviceIoDirect(PIO)

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參考資訊：
1. Source Code

WdfDeviceIoDirect的概念就是直接Mapping User Buffer，然後Driver使用該Mapped的MDL(Memory Description List)操作，相較於WdfDeviceIoBuffered，因為不須I/O Manager更新回User Buffer，因此，效率會比較好，而如果Driver會操作到DMA(Direct Memory Access)記憶體的話，不適用此方式，雖然司徒目前還沒有寫過DMA相關的Windows Driver，不過依據Microsoft的說明文件來看，使用DMA的話，必須使用另一個API(MmGetMdlVirtualAddress)去取得DMA實體記憶體位址，反之，如果不是DMA的操作，就是PIO(Programmed I/O)方式。

記憶體指標：

Event	Buffer	Length
EvtIoRead	Step 1. WdfRequestRetrieveOutputWdmMdl() Step 2. MmGetSystemAddressForMdlSafe()	傳入的第三個參數
EvtIoWrite	Step 1. WdfRequestRetrieveInputWdmMdl() Step 2. MmGetSystemAddressForMdlSafe()	傳入的第三個參數

main.c

#include <ntddk.h>
#include <wdf.h>

#define DEV_NAME L"\\Device\\MyDriver"
#define SYM_NAME L"\\DosDevices\\MyDriver"

char szBuffer[255]={0};

void IrpFileCreate(WDFDEVICE Device, WDFREQUEST Request, WDFFILEOBJECT FileObject)
{  
  DbgPrint("IrpFieCreate");
  WdfRequestComplete(Request, STATUS_SUCCESS);
}

void IrpFileClose(WDFFILEOBJECT FileObject)
{
  DbgPrint("IrpFieClose");
}

void IrpRead(WDFQUEUE Queue, WDFREQUEST Request, size_t Length)
{
  PMDL mdl;
  ULONG len;
  UCHAR *dst;
  WDFMEMORY memory;
  
  DbgPrint("IrpRead");
  len= strlen(szBuffer) + 1;
  WdfRequestRetrieveOutputWdmMdl(Request, &mdl);
  dst= MmGetSystemAddressForMdlSafe(mdl, LowPagePriority);
  memcpy(dst, szBuffer, len);
  WdfRequestCompleteWithInformation(Request, STATUS_SUCCESS, len);
}

void IrpWrite(WDFQUEUE Queue, WDFREQUEST Request, size_t Length)
{
  PMDL mdl;
  UCHAR *src;
  WDFMEMORY memory;
  
  DbgPrint("IrpWrite");
  WdfRequestRetrieveInputWdmMdl(Request, &mdl);
  src= MmGetSystemAddressForMdlSafe(mdl, LowPagePriority);
  memcpy(szBuffer, src, Length);
  DbgPrint("Buffer: %s, Length:%d", szBuffer, Length);
  WdfRequestCompleteWithInformation(Request, STATUS_SUCCESS, Length);
}

NTSTATUS AddDevice(WDFDRIVER Driver, PWDFDEVICE_INIT pDeviceInit)
{
  WDFDEVICE device;
  UNICODE_STRING suDevName;
  UNICODE_STRING szSymName;
  WDF_FILEOBJECT_CONFIG file_cfg;
  WDF_IO_QUEUE_CONFIG ioqueue_cfg;
  
  RtlInitUnicodeString(&suDevName, DEV_NAME);
  RtlInitUnicodeString(&szSymName, SYM_NAME);
  WdfDeviceInitAssignName(pDeviceInit, &suDevName);
  
  WdfDeviceInitSetIoType(pDeviceInit, WdfDeviceIoDirect);
  WDF_FILEOBJECT_CONFIG_INIT(&file_cfg, IrpFileCreate, IrpFileClose, NULL);
  WdfDeviceInitSetFileObjectConfig(pDeviceInit, &file_cfg, WDF_NO_OBJECT_ATTRIBUTES);
  WdfDeviceCreate(&pDeviceInit, WDF_NO_OBJECT_ATTRIBUTES, &device);
  WdfDeviceCreateSymbolicLink(device, &szSymName);
  
  WDF_IO_QUEUE_CONFIG_INIT_DEFAULT_QUEUE(&ioqueue_cfg, WdfIoQueueDispatchSequential);
  ioqueue_cfg.EvtIoRead = IrpRead;
  ioqueue_cfg.EvtIoWrite = IrpWrite;
  return WdfIoQueueCreate(device, &ioqueue_cfg, WDF_NO_OBJECT_ATTRIBUTES, WDF_NO_HANDLE);
}

NTSTATUS DriverEntry(PDRIVER_OBJECT pOurDriver, PUNICODE_STRING pRegistry)
{
  WDF_DRIVER_CONFIG config;

  WDF_DRIVER_CONFIG_INIT(&config, AddDevice);
  return WdfDriverCreate(pOurDriver, pRegistry, WDF_NO_OBJECT_ATTRIBUTES, &config, WDF_NO_HANDLE);
}

IrpWrite()複製User Application的資料到szBuffer
IrpRead()回填資料給User Application

app.c

#define INITGUID
#include <windows.h>
#include <strsafe.h>
#include <setupapi.h>
#include <stdio.h>
#include <stdlib.h>

int __cdecl main(int argc, char* argv[])
{
  HANDLE hFile = NULL;
  DWORD dwRet = 0;
  char szBuffer[255]={0};

  hFile = CreateFile("\\\\.\\MyDriver", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
  if(hFile == INVALID_HANDLE_VALUE){
    printf("failed to open mydriver");
    return 1;
  }

  strncpy(szBuffer, "I am error", sizeof(szBuffer));
  WriteFile(hFile, szBuffer, strlen(szBuffer) + 1, &dwRet, NULL);
  printf("WR: %s, %d\n", szBuffer, dwRet);

  memset(szBuffer, 0, sizeof(szBuffer));
  ReadFile(hFile, szBuffer, sizeof(szBuffer), &dwRet, NULL);
  printf("RD: %s, %d\n", szBuffer, dwRet);
  CloseHandle(hFile);
  return 0;
}

結果

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